However my Freedom of Information requests reveal that the pass was requested by none other than Boris himself for a six month period, renewable.

And rather than being mistakingly authorised by an "admin officer," the pass was personally authorised by his then chief of staff, the late Sir Simon Milton.

And rather than being "swiftly withdrawn" Mr. Crosby retained the pass for almost five months.

London Assembly Labour group leader, Len Duvall, said today:

"We were given completely misleading information about how and why this pass was issued. It says a lot about the mayor and his senior staff that they don't think they need to play by the same rules as everyone else and are happy to give out totally false information to cover things up when they've been found out. It's astounding they thought it was ok to give this Tory campaign organiser full access to the seat of London government."

A spokesperson for the Mayor denied a cover up, saying that:

"We stand by the original statement because the security pass was requested by an admin officer. We sought very hard to find out who had given authorisation for the pass and checked with every director and mayoral advisor but none were aware it, Following a more detailed trawl, prompted by your FOI, it was discovered that the late Sir Simon Milton has authorised the pass. The current Chief of Staff withdrew the pass when he was informed of its existence."

Boris has repeatedly refused to reveal exactly how many meetings he has had with Crosby in City Hall during what should be strictly work hours.

In response to my Freedom of Information request, the Mayor's office claimed that the log detailing exactly when and how often Crosby used his pass was deleted "automatically" after he returned it.